The present invention relates to an endoscope system that is capable of capturing in vivo OCT (Optical Coherence Tomography) images of an object.
Conventionally, endoscope systems for observing objects inside a human cavity have been known. Such an endoscope system is provided with an endoscope, which is to be inserted inside the human cavity, and an illuminative external device, which is to be connected to the endoscope. The external device includes a light source unit for illuminating the object and a processor for processing image signals.
The endoscope includes:
an illuminating optical system, which is connected to the light source unit of the external device and used for illuminating an object (e.g., the paries of a body cavity);
an objective optical system for forming an optical image of the object; and
a CCD (Charge Coupled Device) provided substantially at a focal plane of the objective optical system and electrically connected to the processor of the external device.
At a tip end of the endoscope, an instrument opening is formed. Forceps or various kinds of treatment instruments inserted in the endoscope are protruded from the instrument opening inside the human cavity.
With the endoscope system described above, an operator is capable of observing inside the human cavity. The operator firstly inserts the endoscope inside the human cavity. Light emitted by the light source unit of the external device is projected to an object to be observed through the illuminating optical system. An optical image of the illuminated object is formed, through the objective optical system, on the light receiving surface of the CCD. The CCD converts the received optical image into an electronic image (i.e., image signal), which is transmitted to the processor of the external device. The processor processes the received image signal, and displays the image of the object on a displaying device. Thus, the operator is capable of observing inside the human cavity of a patient through the displaying device.
If the operator judges that there is a possibility of a cancer or a tumor within the observing portion of the human cavity, a forceps or biopsy instrument is inserted in an instrument channel inside the endoscope. The tip portion of the instrument is protruded from the instrument opening, and the tissues of the portion in question are collected. The tissues thus obtained is subjected to a pathological inspection, and based on the results of the inspection, diagnosis is made.
According to the conventional endoscope system as described above, only the surface of the human cavity is observable. In order to know the condition of tissues beneath the paries of the human cavity, biopsy operation is required. In particular, in order to find an early cancer or a small tumor, the biopsy operation is indispensable. However, the pathological inspection requires time, and therefore, the diagnosis requires relatively long time.
Further, in view of a burden to the patient, the biopsy can be done only in a limited area and by a limited number of times. Diseased portion may be present at a portion other than the portion identified by the operator. However, such a portion might be overlooked, and as a result, an accurate diagnosis may not be done even if the pathological inspection is performed.
It is therefore an object of the present invention to provide an improved endoscope system that enables an accurate diagnosis within a relatively short period of time.
For the object, according to the present invention, there is provided an endoscope system, which is provided with a light guide including a plurality of optical paths, a low-coherent light source that emits low-coherent light beams, the low-coherent light source being provided at a proximal end side of the light guide, the light beams emitted by the low-coherent light source being incident on the plurality of optical paths, respectively. The endoscope system is further provided with an interferometer unit having a beam splitting element that splits each of the low-coherent light beams emitted from the distal end of the light guide and emits split one of each of the beams to an object, a reference optical system that guides the other split beam of each of the beams, a reflector unit that reflects the beams guided by the reference optical system toward the beam splitting element, and a light detecting device that detects an interfered beam generated by interference, at the beam splitting element, between the beam reflected by the object and the beam reflected by the reflector unit. The endoscope system is further provided with a driving unit that moves the interferometer unit toward/away from the object, and a signal processing system that generates a tomogram based on the signal detected by the light detecting device.
In such an endoscope system, the driving unit moves the interferometer unit toward/away from the object, that is, the interferometer unit scans the object, in the direction of the depth of the object, and the signal processing system generates a tomogram based on the signal detected by said light detecting device.
Optionally, the reference optical system includes an optical member having a relatively high refractive index. Preferably, the optical member is formed with a non-reflecting surface against the range of wavelength of the low-coherent light beams on the beam splitting element side, and a reflecting surface on the other side.
Alternatively, the reference optical system may have a gradient index optical member whose refractive index is greater at a portion closer to the reflector unit, and smaller at a portion farther from the reflector unit.
In this case, it is preferable that, the refractive index of the gradient index optical member, at abeam splitting element side, has substantially the same refractive index as the beam splitting element.
Still optionally, the interferometer unit is accommodated in the distal end portion of the endoscope.
Further optionally, the driving unit may include a driving force supply that is provided at the proximal end side of the endoscope and supplies driving force, and a force transmitting member that is connected to the driving force supply and the interferometer unit, the force transmitting member transmitting the force supplied by the driving force supply and moves the interferometer unit.
Further optionally, the light guide may be composed of a fiber array having a plurality of single-mode optical fibers arranged in parallel. Optionally, each single-mode optical fibers preserves its polarization.
Optionally, the beam splitting element is a beam splitter prism or an optical fiber coupler.
In this case, the endoscope system may further include a collimating lens array that is formed with a plurality of lens surfaces that collimates each of the beams emitted from the fiber array into parallel light beam, each of the parallel light beams being directed toward the beam splitting element, and a collective lens array including a plurality of lens surfaces that converges one of the parallel beams split by the beam splitting element on the object.
Still optionally, the low-coherent light source may include a super-luminous diode.
Yet optionally, the endoscope system may include an illuminating optical system that emits at least one of visible light, and excitation light which causes biotissues to fluoresce, toward the object, an objective optical system that converges the light from the surface of the object to form an object image; and an image capturing system that captures the optical image formed by the objective optical system.
In this case, the endoscope system may include a visible light source that emits visible light, an excitation light source that emits the excitation light, and a light source switching system that causes one of the visible light and the excitation light to be incident on the illuminating optical system. The objective optical system may form a normal light image of the object when the visible light is incident on the illuminating optical system, and the objective optical system may form a fluorescent light image of the object when the excitation light is incident on the illuminating optical system.
Still optionally, the endoscope system may include a displaying device that displays the object image captured by the image capturing system, and the tomogram generated by the signal processing system. Preferably, the normal light image, the fluorescent light image and the tomogram may be displayed at the same time at different displaying areas defined on the displaying device.